Synthesis and Photoluminescence of Single-Crystalline Fe(III)-Doped CdS Nanobelts.

In this paper, we report the synthesis and optical properties of Fe(III) doped CdS nanobelts (NBs) via simple Chemical Vapor Deposition (CVD) technique to explore their potential in nano-optics. The energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis manifested the presence of Fe(III) ions in the NBs subsequently confirmed by the peak shifting to lower phonon energies as recorded by Raman spectra and shorter lifetime in ns. Photoluminescence (PL) spectrum investigations of the single Fe(III)-doped CdS NBs depicted an additional PL peak centered at 573 nm (orange emission) in addition to the bandedge(BE) emission. The redshift and decrease in the BE intensity of the PL peaks, as compared to the bulk CdS, confirmed the quenching of spectra upon Fe doping. The synthesis and orange emission for Fe-doped CdS NBs have been observed for the first time and point out their potential in nanoscale devices.

Synthesis of Nanocrystalline SnO2 Microspheres and Their Hydrogen Absorption Characteristics.

SnO2 solid microspheres and multilayered nanocrystalline SnO2 hollow microspheres (MHS-SnO2) have been successfully synthesized in the solvothermal environment by using different solvents. The morphology, structure and composition of the as-prepared products are characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED) and X-ray diffraction (XRD). The growth mechanism of SnO2 solid microspheres and MHS-SnO2 are proposed and attributed to the viscosity of solvent. The studies on hydrogen absorption characteristics of SnO2 solid structure and MHS-SnO2 show an absorption capability of 0.50 wt.% and 0.92 wt.%, respectively.

Surgical Embolectomy for Acute Massive and Submassive Pulmonary Embolism in a Series of 115 Patients.

BACKGROUND: Pulmonary embolectomy is often indicated for central pulmonary embolism (PE) with hemodynamic instability, but remains controversial for hemodynamically stable patients with signs of right ventricular dysfunction. Because thrombolytic therapy is often contraindicated postoperatively, we reviewed risk factors and outcomes of pulmonary embolectomy for stable and unstable central PE, particularly in the early postoperative period. METHODS: Between October 1999 and September 2013, 115 patients underwent pulmonary embolectomy for central, hemodynamically unstable PE (49 of 115, 43%) or hemodynamically stable PE (56 of 115, 49%). Ten operations for alternate indications (right atrial mass, endocarditis) were excluded for comparison analysis, leaving 105 patients. RESULTS: Mean age was 59 ± 13 years; 46 of 105 patients (44%) had recent surgery (within 5 weeks): orthopedic (12 of 46, 25%), neurosurgery (11 of 46, 24%), or general surgery (10 of 46, 22%). Preoperative demographics did not differ between groups, except for the frequency of cardiopulmonary resuscitation among unstable patients (11 of 49, 22%) versus stable patients (0 of 56, 0%; p < 0.001). Operative mortality for the combined groups was 6.6% (7 of 105): unstable 10.2% (5 of 49) versus stable 3.6% (2 of 56; p = 0.247). Of 11 patients requiring preoperative cardiopulmonary resuscitation, 4 died. Six-month, 1-year, and 3-year survival rates were, respectively, 75%, 68.4%, and 65.8% for unstable PE, and 92.6%, 86.7%, and 80.4% for stable PE (p = 0.018). CONCLUSIONS: This large series of pulmonary embolectomies demonstrates excellent early and late survival rates for patients with stable PE and unstable PE. These findings confirm pulmonary embolectomy as a beneficial therapeutic option for central PE, especially during the postoperative period when thrombolytic therapy is often contraindicated.

The impact of a minimally invasive approach on reoperative aortic valve replacement.

BACKGROUND AND AIM OF THE STUDY: The advantages of minimally invasive aortic valve replacement (AVR) are well documented, but whether the benefits extend to subsequent reoperative aortic valve surgery and beyond is unknown. The study aim was to compare in-hospital outcomes and long-term survival following reoperative AVR between patients who had previous undergone either minimally invasive AVR (mini-AVR) or full sternotomy AVR (sAVR). METHODS: All reoperative, isolated AVRs performed between July 1997 and September 2013 at the authors' institution, with or without non-complex aortic surgery, were identified. Patients were excluded if AVR was not isolated, had occurred prior to July 1997, or if the initial AVR was performed before the patient was aged 18 years. All reoperations were performed through a full sternotomy. The main outcomes of interest were operative results and long-term survival. RESULTS: A total of 101 patients was identified, of which 34 had undergone previous mini-AVR and 67 previous sAVR. The time from the previous AVR was similar in both groups (median 7.6 years overall). Of previous valve implants, 57 were bioprostheses and 44 mechanical; structural valve degeneration was the most common indication for surgery (43/101). Mini-AVR and sAVR patients did not differ significantly with regards to patient demographics and preoperative risk factors. A strong trend towards shorter skin-to-skin operative times was observed for mini-AVR (330 min versus 356 min; p = 0.053). Postoperatively, mini-AVR patients had a shorter ventilation time (5.7 h versus 8.4 h; p = 0.005), intensive care unit stay (37 h versus 63 h; p ≤ 0.001) and hospital length of stay (6.5 days versus 8.0 days; p = 0.038). There was one operative mortality in the sAVR, and none in the mini-AVR group. Mid-term survival at one and five years for mini-AVR was 100% (95% CI 100-100) and 100% (95% CI 100-100), and for sAVR was 93.9% (95% CI 88.2-99.7) and 85.0% (95% CI 75.1-94.9), respectively (p = 0.041). CONCLUSION: Mini-AVR confers benefits during subsequent reoperative AVR, with shorter hospital stays and improved long-term survival. These findings suggest that mini-AVR should be considered for patients at risk for aortic valve reoperation, and describes a previously unreported advantage of this well-established technique.

The safety of deep hypothermic circulatory arrest in aortic valve replacement with unclampable aorta in non-octogenarians.

OBJECTIVES: Aortic valve replacement (AVR) in patients with severely atherosclerotic aortas (porcelain aorta) presents a significant technical challenge. Two strategies are deep hypothermic circulatory arrest (DHCA) during conventional surgery and transcatheter aortic valve replacement (TAVR). The aim of this study was to examine the outcomes in patients who underwent DHCA for AVR with a porcelain aorta to identify whether older patients are more suitable for TAVR. METHODS: Between October 2004 and December 2012, 122 patients underwent AVR using DHCA for atherosclerotic aorta. Patients with concomitant valve surgery were excluded. Overall, 63.9% (78/122) were of age <80 (non-octogenarian group, NOG) and 36.1% (44/122) were >80 (octogenarian group, OG). Of the total cohort, 62.3% (76/122) had concomitant coronary artery bypass graft surgery. RESULTS: The mean age for the whole cohort was 75.7 ± 8.5 years; 70.2 ± 8.1 years for the NOG and 83.4 ± 2.6 years for the OG (P = 0.001). The OG had a higher rate of preoperative renal failure (20.5%, 9/44 vs 7.7%, 6/78, P = 0.048) and trends towards a greater history of cerebrovascular disease (9.1%, 4/44 vs 1.3%, 1/78, P = 0.056), but fewer reoperations (6.8%, 3/44 vs 19.2%, 15/78, P = 0.069). Cardiopulmonary bypass time, aortic cross-clamp time and circulatory arrest time were similar between the two groups. Postoperative complication rates were similar except for permanent stroke (OG 18.2%, 8/44 vs NOG 6.4%, 5/78, P = 0.065). The overall operative mortality rate was 8.2% (10/122); however, the OG had significantly higher operative mortality compared with the NOG (15.9%, 7/44 vs 3.8%, 3/78, P = 0.035). One- and 5-year survival rates were 88.9 and 79.3% for the NOG versus 75.0 and 65.9% for the OG (P = 0.027), respectively. CONCLUSIONS: Postoperative neurological events and operative mortality were, respectively, 3- and 4-fold higher in octogenarians undergoing AVR using DHCA. Such patients may represent suitable candidates for TAVR if favourable outcomes are demonstrated in patients with atherosclerotic aortas. Surgical AVR remains the standard treatment option with excellent outcomes for patients <80 years old with unclampable aortas.

Mechanical versus bioprosthetic mitral valve replacement in patients <65 years old.

OBJECTIVE: Because of its durability, the mechanical valve is typically chosen for young patients undergoing mitral valve replacement (MVR). However, a bioprosthetic valve might have the benefit of valve-in-valve transcatheter valve replacement when valve failure occurs. We examined the outcomes in patients who had undergone mechanical valve MVR (MVRm) versus bioprosthetic valve MVR (MVRb) in patients aged <65 years. METHODS: A total of 768 consecutive patients aged <65 years, who had undergone MVR from January 1991 to June 2012 were identified. Propensity matching was used to derive a case-control subset for analysis. Long-term outcomes were collected by chart review, routine patient follow-up, and query of the Social Security Death Index. The postoperative and long-term outcomes of interest included combined stroke and embolic events, reoperations, and mortality. RESULTS: Of 768 consecutive patients, 627 were in the MVRm and 141 in the MVRb group. Propensity score matching yielded a cohort of 125 MVRb (89%) and 125 control MVRm patients with similar etiology mixes. The groups were similar in age (MVRm, 53.2 ± 9.0 years; MVRb, 53.8 ± 10.6 years; P = .617) and other preoperative characteristics. The postoperative outcomes were also similar between the 2 groups, including reoperation for bleeding, stroke, deep sternal infection, sepsis, and length of hospital stay. The operative mortality was also similar (MVRm, 5.6%; MVRb, 8.0%; P = .617). However, Kaplan-Meier analysis showed the MVRb group had a greater reoperation rate (P = .001) and shorter estimated survival (11.3 vs 13.5 years, P = .004). The incidence of bleeding and stroke or embolic events between the 2 groups was similar. CONCLUSIONS: In the present report, MVRb for patients <65 years old was associated with a high reoperation rate and decreased survival. Although a future transcatheter valve-in-valve technique for a failed bioprosthetic valve might reduce the risk of reoperation, this finding confirms the safety of mechanical valves in this group.

Influence of SiO2 on the structure-controlled synthesis and magnetic properties of prismatic MnO2 nanorods.

Silicon dioxide-doped tetragonal MnO2 single crystalline prismatic nanorods have been successfully synthesized through a facile hydrothermal route at a temperature of 250 ° C with a reaction time as quick as 5 h. The synthesized MnO2 prismatic nanorods were characterized by x-ray diffraction, field emission scanning electron microscopy, energy dispersive x-ray analysis, transmission electron microscopy, high resolution transmission electron microscopy with selected area electron diffraction and Raman spectroscopy. Experimental results show that single crystalline tetragonal MnO2 nanorods have been successfully synthesized at all doping concentrations and that nanorods with a prismatic surface morphology have been obtained at 20 mass% of SiO2. The diameter of as-prepared MnO2 nanorods increases from 125 to 250 nm on increasing the dopant concentration. X-ray photoelectron spectroscopy analysis confirms the presence of valence Si (2p) of SiO2 in the as-prepared MnO2 nanostructures. The intensity of Raman modes clearly increases with increasing doping concentration, indicating an improvement in the structural aspects of the MnO2 nanorods. The magnetic properties of the products have been evaluated using a vibrating sample magnetometer, revealing that the as-prepared MnO2 nanorods exhibit weak ferromagnetic behavior at room temperature. The Néel temperature of the as-obtained products is calculated as 97 K. On the basis of the structural information, a growth mechanism is proposed for the formation of prismatic-like 1D MnO2 nanorods.

Controlled synthesis, characterizations and structural-properties of micro-flowers, pine-cone, core-shell and liver-like micro-architecture of crystalline ZnMn2O4.

The conspicuous ZnMn2O4 micro-structures have been synthesized by hydrothermal method by using Mn3O4 and Zn powder as precursors. The micro-structures of the ZnMn2O4 could be tuned by changing the reaction time only in the reaction system. The final products have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and the Raman spectroscopy. Room temperature Raman spectroscopy investigation indicates that the synthesized micro-structures have strong fundamental vibrational modes. The intensity of the vibrational modes varied with change in the reaction time in the synthesized products of ZnMn2O4. The mechanism of this peculiar Raman property was analyzed.

Effect of atomic percentage of Zn on the size and optical properties of porous ZnMn2O4 nanoparticles.

The porous ZnMn2O4 nanostructures have been synthesized by hydrothermal method by using Mn3O4 and Zn powder as precursors. The morphology of the nanoparticles could be tuned by changing the molar ratio of Zn in the reaction system. The final products have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, UV-visible spectroscopy and the florescence spectrometer. Room temperature photoluminescence investigation indicates that the nanostructures have strong band-gap emission at yellow and orange bands. Absorption properties of ZnMn2O4 nanostructures indicated that the band gap energy varied with change in the atomic percentage of Zn in hetaerolite ZnMn2O4. The mechanism of this peculiar optical property was analyzed.

Preparation, characterizations and optical property of single crystalline ZnMn2O4 nanoflowers via template-free hydrothermal synthesis.

In this work, we have reported a template-free hydrothermal approach to fabricate highly pure single phase ZnMn2O4 pen-type nano needles assembled with flower type nanostructures. The X-Ray Diffraction, Scanning Electron Microscopy, Energy Dispersive X-Ray spectroscopy, Raman Spectroscopy, Transmission Electron Microscopy, High Resolution Transmission Electron Microscopy, Selected Area Electron Diffraction and UV-visible spectroscopy techniques were used to study the structural and optical properties of Pen-type nanoneedles assembled with flower like nanostrucutres. Single crystalline hetaerolite ZnMn2O4 pen type nanoneedles of flower like nanostructures have an average diameter of 250 nm. Room temperature Raman spectroscopy reveals the four fundamental vibrational modes. Room temperature UV-vis spectrometer was used to determine the transmittance behaviour pen type nanoneedles of flower like nanostructures. Direct optical band gap of 2.19 eV was acquired by using Davis-Mott model. The UV-visible spectrum points out that the absorption is prominent in visible region and transparency is more than 80% in UV region.

Synthesis, characterization and optical property of shrimps-like nanostructures of MnO2 by hydrothermal route.

Hexagonal MnO2 shrimps like nanostructures have been successfully synthesized through a facile hydrothermal route at a temperature of 175 degrees C. The synthesized MnO2 nanostructures were characterized by the X-Ray Diffraction, Scanning Electron Microscopy, Energy Dispersive X-Ray spectroscopy, Transmission Electron Microscopy, High Resolution Transmission Electron Microscopy, Selected Area Electron Diffraction and UV-visible spectroscopy. UV-vis spectrophotometer was used to determine the absorption behaviour of shrimps like nanostructures. Direct optical band gap of 1.65 eV was acquired by using Davis-Mott model. The UV-visible spectrum exhibited the prominent absorption in visible region.